Mobile communication systems were developed to provide subscribers with voice communication services on the move. Recently, mobile communication systems have evolved beyond the early voice-oriented services to the level of supporting high speed data communication services. However, resource shortages and user requirements for higher speed services have spurred evolution towards increasingly more advanced mobile communication systems.
In order to meet the increasing demand for wireless data traffic since the commercialization of 4G communication systems, the development focus is on the 5th Generation (5G) or pre-5G communication system. For this reason, the 5G or pre-5G communication system is called a beyond 4G network communication system or post Long Term Evolution (LTE) system.
In order to accomplish high data rates, consideration is being given to implementing the 5G communication system on the millimeter Wave (mm Wave) band (e.g., 60 GHz band). In order to mitigate propagation loss and increase propagation distance, the 5G communication system is likely to accommodate various techniques such as beamforming, massive MIMO, Full Dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large scale antenna.
Also, for throughput enhancement of the 5G communication system, research is being conducted on various techniques such as small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, Device to Device (D2D) Communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation.
Furthermore, the ongoing research includes the use of Hybrid FSK and QAM Modulation (FQAM) and Sliding Window Superposition Coding (SWSC) as Advanced Coding Modulation (ACM), Filter Bank Multi Carrier (FBMC), Non-Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA).
The mobile communication system has evolved to a high-speed, high-quality wireless packet data communication system capable of providing data and multimedia services beyond the early voice-oriented services. The standardization organizations such as the 3rd Generation Partnership Project (3GPP), the 3rd Generation Partnership Project-2 (3GPP2), and the Institute of Electrical and Electronics Engineers (IEEE) have standardized 3rd Generation mobile communication systems based on multicarrier multiple-access schemes. Recently, various multicarrier-based mobile communication standards such as 3GPP Long Term Evolution (LTE), 3GPP2 Ultra Mobile Broadband (UMB), and IEEE 802.16m have been developed to meet the requirements of the high-speed, high-quality wireless packet data communication services.
The existing 3G wireless packet data communication systems LTE, UMB, and 802.16m operate based on multicarrier multiple access schemes and adopt various techniques such as Multiple-Input Multiple-Output (MIMO), beamforming, Adaptive Modulation and Coding (AMC), and Channel-Sensitive Scheduling to improve the transmission efficiency. The above techniques are capable of improving transmission efficiency and system throughput in such a way that data rates are adjusted by concentrating transmission power to certain antennas according to the channel quality and transmitting data selectively to the user with a high channel quality. Since most of these techniques operate based on the CSI between a base station (BS) (hereinafter, interchangeably referred to as an evolved Node B (eNB)) and a terminal (hereinafter, interchangeably referred to as a User Equipment (UE) or Mobile Station (MS)), it is necessary for the base station or the terminal to measure the channel state therebetween using a reference signal such as a Channel State Indication Reference Signal (CSI-RS). The eNB denotes a device located at a certain place for downlink transmission and uplink reception, and one eNB may take charge of a plurality of cells. A mobile communication system is comprised of a plurality of eNBs distributed geometrically, and each eNB can accommodate a plurality of cells for communicating signals.
Meanwhile, in recent years research has been conducted on transmission/reception schemes more efficient than Orthogonal Frequency Division Multiplexing (OFDM). As a consequence, the research focus has moved from studying the orthogonal waveform design represented by OFDM to studying a bi-orthogonal waveform design characterized by reduced orthogonality and narrow spectrum, such as Bi-orthogonal Frequency-Division Multiplexing (BFDM), and a non-orthogonal waveform design, such as Universal Filtered Multi-Carrier (UFMC); however, for use of a non-orthogonal waveform with reduced orthogonality, there is a need of a feedback method capable of improving communication efficiency.